CHAPTER XXIV.. Snow. Hail. Rain.

SNOW. HAIL. RAIN.

Q. What is SNOW?

A. The condensed vapour of the air frozen, and precipitated to the earth.

Q. What is the CAUSE of SNOW?

A. When the air is nearly saturated with vapour, and condensed by a current of air below freezing point, some of the vapour is squeezed out, and frozen into snow.

A few years ago, some fishermen (who wintered at Nova-Zembla), after they had been shut up in a hut for several days, opened the window, and the cold external air rushing in, instantly condensed the air of the hut, and the vapour (which was squeezed out) fell on the floor in a shower of snow.

Q. Why does SNOW fall in WINTER time?

A. Because the sun's rays are too oblique to heat the surface of the earth; and (as the earth has no heat to radiate into the air) the air is very cold.

Q. What is SLEET?

A. When flakes of snow (in their descent) pass through a bed of air above freezing point, they melt; and fall to the earth as half-melted snow or sleet.

Q. What is the USE of SNOW?

A. To keep the earth warm, and to nourish it.

Q. How can snow keep the EARTH WARM?

A. Because it is a very bad conductor; in consequence of which, the earth which is covered with snow, very rarely descends below freezing point, even when the air is 15 or 20 degrees colder.

Q. Why is SNOW a BAD CONDUCTOR of heat and cold?

A. Because air is confined and entangled between the crystals, and air is a very bad conductor; when, therefore, the earth is covered with snow, it cannot throw off its heat by radiation.

Q. Tell me the words of the PSALMIST (cxlvii. 16.) respecting snow, and explain what he means.

A. The Psalmist says--"The Lord giveth snow like wool:" and he means not only that snow is as white as wool, but that it is also as warm as wool.

Q. Why is WOOL WARM?

A. Because air is entangled between the fibres of the wool, and air is a bad conductor.

Q. Why is SNOW WARM?

A. Because air is entangled between the crystals of the snow, and air is a bad conductor.

Q. Why does SNOW NOURISH the earth?

A. Because it supplies it with moisture for a considerable time; which penetrates slowly into the soil, and insinuates itself through every clod, ridge, and furrow.

Q. Why is there NO SNOW in SUMMER time?

A. No snow reaches the general surface of the earth in summer time, because the heat of the earth melts it in its descent.

Q. Why are some MOUNTAINS ALWAYS COVERED with SNOW?

A. 1st--Because the air is more rarefied; and rarefied air abstracts heat which it holds in a latent state:

2ndly--As the mountain top is not surrounded by earth to radiate heat into the air; therefore, the snow is not melted in its descent, but falls on the mountain, and lies there.

Q. Why is SNOW WHITE?

A. Snow is formed of an infinite number of very minute crystals and prisms, which reflect all the colours of the rays of light; and these colours uniting before they meet the eye, cause snow to appear white.

Q. What is HAIL?

A. Rain, which has passed in its descent through some cold bed of air, and has been frozen into drops of ice.

Q. Why is ONE bed of air COLDER than another?

A. This is frequently caused by electricity in the air, unequally distributed.

Q. Why is HAIL frequently accompanied with THUNDER and LIGHTNING?

A. 1st--Because the congelation of water into hail disturbs the electricity of the air: and

2ndly--The friction (produced by the fall of hail) excites it still more.

Q. Why does HAIL fall generally in SUMMER and AUTUMN?

A. 1st--Because the air is more highly electrified in summer and autumn: and

2ndly--The vapours (being rarefied) ascend to the more elevated regions, where the cold is greater than it is nearer the earth.

Q. What TWO things are essential to cause HAIL?

A. Two strata of clouds having opposite electricities, and two currents of wind. The lower cloud (being negative) is the one precipitated.

Q. What is RAIN?

A. The vapour of the clouds or air condensed, and precipitated to the earth.

Q. Why is the vapour of the air or clouds PRECIPITATED?

A. When the air is saturated with vapour, if a cold current condenses it, it is no longer able to hold all its vapour in solution, and some of it is squeezed out, and falls as rain.

Q. Why does RAIN fall in DROPS?

A. The vapoury particles in their descent attract each other; and those which are sufficiently near, unite and form into a drop.

Q. Why does not the COLD of NIGHT ALWAYS cause rain?

A. When the air is not near saturation (although condensed by the chill of evening), it will still be able to hold its vapour in solution.

Q. Why does a PASSING CLOUD often drop RAIN?

A. Because the cloud (travelling about on the wind) comes into contact with something that chills it; and its vapour being squeezed out, falls to the earth as rain.

Q. Why are RAIN-DROPS sometimes much LARGER than at OTHER times?

A. When the rain-cloud is floating near the earth, the drops are large, because such a cloud is much more dense than one which is more elevated.

The size of the rain-drop is increased according to the rapidity with which the vapours are condensed.

Q. Does not WIND sometimes INCREASE the SIZE of rain-drops?

A. Yes; by blowing two or more drops into one.

Q. Why do CLOUDS FALL in RAINY weather?

A. 1st--Because the clouds are heavy with abundant vapour: and

2ndly--As the density of the air is diminished, it is less able to buoy the clouds up.

Q. How do you KNOW that the DENSITY of the air is DIMINISHED in RAINY weather?

A. Because the mercury of a barometer falls.

Q. Why is RAIN-water more FERTILIZING than PUMP-water?

A. Because it contains a compound of hydrogen and nitrogen (called ammonia), which is a very excellent food for young plants.

Q. Why is NOVEMBER made by God to be a RAINY MONTH?

A. Because rain hastens the putrefaction of the fallen leaves by causing fermentation.

Q. Why does RAIN PURIFY the AIR?

A. 1st--Because it beats down the noxious exhalations collected in the air, and dissolves them:

2ndly--It mixes the air of the upper regions with that of the lower regions: and

3rdly--It washes the earth, and sets in motion the stagnant sewers and ditches.

Q. Why are MOUNTAINOUS countries more RAINY than flat ones?

A. The air (striking against the side of the mountains) is carried up the inclined plane, and brought in contact with the cold air of the higher regions, by which it is condensed, and its vapour squeezed out.

Q. Why does a SPONGE SWELL when it is WETTED?

A. Because the water penetrates the pores of the sponge, and drives the particles of the sponge further from each other; in consequence of which, the bulk of the sponge is greatly increased.

Q. Why do FIDDLE-strings SNAP in WET weather?

A. Because the moisture of the air (penetrating the string) causes it to swell; and (as the cord thickens) its tension is increased, and the string snaps.

Q. Why does PAPER PUCKER when it is WETTED?

A. Because the moisture (penetrating the paper) drives its particles further apart; and (as the moisture is absorbed unequally by the paper) some parts are more enlarged than others; in consequence of which, the paper blisters or puckers.

Q. Why do the weather toys called CAPU'CHINS lift the cowl over the figures in wet weather, and remove it in dry?

A. The cowl of the capu'chin is fastened to a piece of cat-gut. When the weather is wet, the moisture swells the cat-gut and it is shortened, by which means the cowl is pulled up; but in dry weather, the string is loosened, and the cowl falls down.

Q. In another weather toy, the MAN comes out in WET weather, and the LADY in FINE:--Why is this?

A. The two figures are attached to a piece of cat-gut in such a manner, that when the cat-gut is shortened by moisture, it pulls the man out; but when it is loose, the woman falls out by her own weight.

Q. Why are WET STOCKINGS DIFFICULT to PULL ON?

A. The moisture (by penetrating the threads of the stockings) causes them to shrink in size.

Q. What is the MOST RAINY spot in ENGLAND?

A. Keswick (in Cumberland); and then Kendal (a market town in Westmoreland).

(In Keswick, about 63 inches of rain fall in a year. In Kendal, 58; Manchester, 38; Liverpool, 34; Dublin and Cambridge, 25; Lincoln, 24; London, 21; and in Paris, only 18.)

Q. In which PART of the DAY does the MOST RAIN fall?

A. More rain falls by night than by day; because the cold night condenses the air, and diminishes its capacity for holding vapour in solution.

Q. Does more rain fall in SUMMER or in WINTER time?

A. There are more rainy days from September to March; but heavier rains between March and September.

Q. Why are there MORE RAINY DAYS from September to March, than from March to September?

A. Because the temperature of the air is constantly decreasing, and its capacity for vapour decreases also; in consequence of which, it is perpetually obliged to part with some of its vapour in rain.

Q. In what PART of the WORLD does RAIN fall MOST ABUNDANTLY?

A. Near the equator; and the quantity of rain decreases as we approach the poles.

Q. Why does MORE RAIN fall at the EQUATOR than at the POLES?

A. Because the contrast between the night and day is very great. The hot air absorbs moisture very abundantly during the day; and when the cold night condenses the air, it is unable to retain the moisture imbibed, and some of it falls in rain.